Patient-specific pelvic implants for acetabular reconstruction

ABSTRACT

A pelvic implant includes a first surface including a recess configured for receiving a portion of a flange of an acetabular cage and a patient-specific second surface opposite to the first surface. The patient-specific second surface is preoperatively configured from a three-dimensional digital image of a pelvis of a patient to mate and closely conform to a corresponding surface of the pelvis under the flange in only one position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 13/197,851 filed on Aug. 4, 2011, now U.S. Pat. No. ______. The entire disclosure of the above application is incorporated herein by reference.

INTRODUCTION

The present teachings provide various patient-specific pelvic implants. The patient-specific pelvic implants can be spacers for revision acetabular implants used in acetabular reconstruction surgery, such as, for example, protrusio cages or acetabular cages that include an acetabular cup and one or more flanges coupled to the acetabular cup. The patient-specific spacers are prepared preoperatively for the specific patient based on medical scans of the relevant pelvic anatomy of the patient and are configured to be positioned under the flanges of the revision acetabular implants and register and mate with the corresponding pelvic anatomy of the patient in only one position.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

The present teachings provide a pelvic implant that includes a first surface and a patient-specific second surface opposite to the first surface. The first surface has a recess configured for receiving a portion of a flange of an acetabular cage. The patient-specific second surface is preoperatively configured from a three-dimensional digital image of a pelvis of a patient to mate and closely conform to a corresponding surface of the pelvis under the flange in only one position.

In some embodiments, the pelvic implant includes an acetabular cage having a flange and a patient-specific spacer. The patient-specific spacer has a first surface with a recess configured to receive a portion of the flange and a second surface opposite to the first surface. The second surface is patient-specific and preoperatively configured from a three-dimensional digital image of a pelvis of a patient to mate and closely conform as a negative to a corresponding surface of the pelvis under the flange in only one position.

The present teachings also provide a pelvic implant that includes an acetabular cage implantable into a pelvis of a patient and a plurality of patient-specific spacers. The acetabular cage includes an acetabular cup and a plurality of flanges coupled to the acetabular cup. Each spacer has a recess receiving a portion of a corresponding flange of the plurality of flanges and a patient-specific surface. The patient-specific surface is preoperatively configured from a three-dimensional digital image of the pelvis of the patient to mate and closely conform to a corresponding surface of the pelvis under the flange in only one position.

In some embodiments, the pelvic implant can include an acetabular cup and a patient-specific flange modularly coupled to the acetabular cup. The patient-specific flange has a patient-specific surface preoperatively configured from a three-dimensional digital image of the pelvis of the patient to mate and closely conform as a negative to a corresponding surface of the pelvis under the flange in only one position.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a perspective view of a pelvis of a patient;

FIG. 2 is a perspective view of an exemplary acetabular cage;

FIGS. 3A-3C are perspective views of patient-specific spacers for the acetabular cage of FIG. 2 according to the present teachings;

FIGS. 4A-4C are additional perspective views of the patient-specific spacers of FIGS. 3A-3C;

FIGS. 5-7 are different environmental perspective views of the spacers of FIGS. 3A-3C shown with the acetabular cage of FIG. 2 according to the present teachings;

FIG. 8 is a perspective view of another exemplary acetabular cage shown with patient-specific spacers according to the present teachings;

FIG. 9 is an environmental perspective view of the patient-specific spacers shown with the acetabular cage of FIG. 8 according to the present teachings; and

FIG. 10 is an exploded perspective view of an acetabular cup with a patient-specific flange according to the present teachings.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Exemplary embodiments will now be described more fully with reference to the accompanying drawings.

The present teachings generally provide patient-specific pelvic implants. The pelvic implants include patient-specific spacers for revision acetabular implants used in acetabular reconstruction surgery, including, for example, acetabular cages having acetabular cups with flanges or protrusio cages. The patient-specific spacers are prepared preoperatively for the specific patient based on medical scans of the relevant pelvic anatomy of the patient and positioned under the flanges of the revision acetabular implants.

Generally, patient-specific devices including implants and/or patient-specific instruments can be designed preoperatively using computer-assisted image methods based on three-dimensional images of the patient's joint anatomy reconstructed from MRI, CT, ultrasound, X-ray, or other medical scans of the patient's anatomy. Various CAD programs and/or software can be utilized for three-dimensional image reconstruction, such as, for example, software commercially available by Materialise USA, Plymouth, Mich.

Various pre-operative planning procedures are disclosed in commonly assigned and co-pending U.S. patent application Ser. No. 11/756,057, filed May 31, 2007, U.S. patent application Ser. No. 12/103,824, filed Apr. 16, 2008; U.S. patent application Ser. No. 12/371,096, filed Feb. 13, 2009, U.S. patent application Ser. No. 12/483,807, filed Jun. 12, 2009; U.S. patent application Ser. No. 12/872,663, filed Aug. 31, 2010, U.S. patent application Ser. No. 12/973,214, filed Dec. 20, 2010, and U.S. patent application Ser. No. 12/978,069, filed Dec. 23, 2010. The disclosures of the above applications are incorporated herein by reference.

In the preoperative planning stage for acetabular reconstruction, a preoperative surgical plan is formulated for a specific patient with interactive input from the patient's surgeon or other medical professional. Imaging data of the relevant anatomy of a patient can be obtained at a medical facility or doctor's office, using any of the medical imaging methods described above. The imaging data can include, for example, various medical scans of a relevant joint portion or other relevant portion of the patient's anatomy, as needed for joint or other anatomy modeling and, optionally, for determination of an implant alignment axis or for other alignment purposes. The imaging data thus obtained and other associated information can be used to construct a three-dimensional computer (digital) image of the joint or other portion of the anatomy of the patient, such as, in the present application, the patient's pelvis including the acetabular socket. The three-dimensional digital image of the patient's anatomy is used to formulate a preoperative surgical plan for the patient. The preoperative surgical plan includes the design and construction of implants and/or instruments according to selected methods of surgical preparation and implantation.

Generally, the patient-specific spacers and/or other patient-specific implants of the present teachings are configured to match the pelvic anatomy of a specific patient and are generally designed and configured using computer modeling based on the patient's reconstructed three-dimensional digital image of the patient's pelvic anatomy. The patient-specific implants have a pelvis engagement surface that is configured to conformingly contact and match a corresponding pelvic surface of the patient (with or without cartilage or other soft tissue), using the reconstructed three-dimensional digital image of the patient's pelvic anatomy and the computer methods discussed above. In this respect, a patient-specific implant can register and nestingly mate with the corresponding bone surface (with or without articular cartilage) of the specific patient in only one position.

In reconstructive or revision acetabular surgery, the old acetabular implant is removed from the pelvic bone or pelvis 80 and the acetabular area is prepared for a new acetabular implant. Soft tissue may be removed from the acetabular socket 82, from the acetabular rim 84 and from adjacent areas of the ilium 86, ischium 88 and pubic bone 90 (see FIG. 1). The pelvis 80 can be inspected for defects that will require the use of augments and other defect-correcting implants. The acetabular socket 82 can be reamed in preparation for receiving an acetabular cage (revision acetabular implant) that includes an acetabular cup (or shell or dome) with integral or modular flanges. An exemplary acetabular cage 100 is illustrated in FIG. 2. Various acetabular cages similar to the acetabular cage of FIG. 2 are commercially available from Biomet Manufacturing Corp., Warsaw, Ind. The acetabular cage 100 can include an acetabular cup 102 having a generally semi-spherical shape bounded by a cup rim 110.

The acetabular cage 100 is illustrated as having three flanges in this exemplary embodiment, although a different number of flanges and/or other hook or blade elements can be included. Referring to FIG. 2, first and second iliac flanges 104, 106 and an ischial flange 108 are illustrated. In this exemplary embodiment, the first iliac flange 104 has a first (proximal) portion 105 extending from the cup rim 110 and a second (distal) portion 107 that is square-like with four fixation holes 116 for fixation fasteners 111 (see FIG. 5) arranged to form a substantially square or square-like shape. The second iliac flange 106 has a first (proximal) portion 122 extending from the cup rim 110 and a second (distal) portion 121 that has an elongated rectangular shape with two fixation holes 118 arranged along the elongated rectangular shape. In some embodiments, the first portions 105 and 122 of the first and second iliac flanges 104, 106 can be continuous or unitary such that the first and second iliac flanges 104, 106 can be in the form of a single bifurcated iliac flange. The third or ischial flange 108 has a first (proximal) portion 126 extending from the cup rim 110 and a second (distal) portion 123 that has a triangular shape with two fixation holes 120. In the illustration of FIG. 2, the fixation holes 120 are oriented along one side of the second portion 123 and are offset from a centerline of the ischial flange 108. It will be appreciated, however, that the various fixation holes 116, 118, 120, their arrangements on the flanges 104, 106, 108 and the shapes and number of the flanges can vary for different acetabular cages 100.

The acetabular cup 102 can also include an apical hole 112 for coupling with an acetabular inserter. Various fixation holes 114 can be provided through the acetabular cup 102 for selective use with screws or other fixation fasteners by the surgeon. Fixation holes 124 for fixation fasteners can also be provided along the first portions 105, 122, 126 of the corresponding first, second and third flanges 104, 106, 108. The convex bone-engaging surface of the acetabular cup 102 can be coated with porous coating, such as a titanium alloy plasma spray porous coating commercially available from Biomet Manufacturing Corp., Warsaw, Ind.

Referring to FIGS. 3A, 3B and 3C (top side perspective views) and 4A, 4B and 4C (bottom side perspective views), exemplary embodiments of first, second and third patient-specific spacers (or shims) 200A, 200B, 200C (referenced collectively as 200) are illustrated. The patient-specific spacers 200A, 200B, 200C are configured for the first, second and third flanges 104, 106,108 and also for the underlying anatomy of the specific patient, as determined by the three-dimensional digital image reconstruction of the pelvis of the patient from medical scans of the patient, as discussed above. More specifically, each patient-specific spacer 200A, 200B, 200C includes first and second opposing surfaces 204 and 220, a peripheral surface 202 between the first and second surfaces 204, 220 and various fixation holes 210 (or 210A, 210B, 210C) corresponding to the fixation holes of the respective flanges 104, 106, 108. The peripheral surface 202 forms an elevated ridge 206, such that the ridge 206 and the first surface 204 form a slot or recess 207 (collectively for 207A, 207B, 207C) for receiving a second portion of a corresponding flange 104, 106, 108, as discussed below.

Referring to FIGS. 3-7, the recess 207 of each patient-specific spacer 200A, 200B, 200C is configured during the preoperative plan to receive slidably or in a press-fit manner the second or distal portion 107, 121, 123 of the corresponding flange 104, 106, 108. In the exemplary illustrations, the recess 207A of the first spacer (or first iliac spacer) 200A is square-shaped to receive the second portion 107 of the first iliac flange 104. Similarly, the recess 207B of the second spacer (or second iliac spacer) 200B is shaped as an elongated rectangle to receive the second portion 121 of the second iliac flange 106. The recess 2070 of the third spacer (or ischial spacer) 200C is shaped as a triangle to receive the second portion 126 of the ischial (third) flange 108.

With continued reference to FIGS. 3-7, the second surface 220 is a patient-specific bone-engaging surface that is configured during the preoperative plan to register in only one position and mate in a complementary manner (i.e., as a negative or mirror surface) to the iliac and ischial portions of the pelvis 80 that are under the corresponding iliac and ischial flanges 104, 106, 108, when the acetabular cage 100 is implanted. As can be seen in FIGS. 5-7, the patient-specific spacers 200 have a thickness h (i.e., height h of peripheral surface 202) that is substantially greater than the thickness of the flanges 104, 106, 108, although the thickness h can be variable depending on the pre-planned location of the spacer 200 relative to the pelvis 80. For example, in the embodiments of FIGS. 3-7, the first and second spacers 200A, 200B are iliac spacers and have a substantially variable thickness h, while the third spacer 200C is an ischial spacer and is shown with a substantially constant thickness. It should be appreciated, however that the thickness h of the spacers is also determined during the preoperative plan according to the anatomy of the specific patient and the surgeon-selected location for the flanges 104, 106, 108. Accordingly, the thickness h can vary in a patient-specific manner. Accordingly, the spacers 200 can provide reinforcement for the corresponding flanges 104, 106, 108. Further, the flanges 104, 106, 108 themselves can be configured with greater thickness and rigidity, because using their patient-specific spacers 200 makes it unnecessary to make the flanges 104, 106, 108 bend to engage the patient's pelvis 80. The acetabular cage 100 itself, including the location, number and shape of the various iliac and ischial flanges (such as flanges 104, 106, 108) in combination with the corresponding patient specific spacers 200 can be determined and selected during the preoperative plan based on the patient's anatomy and with surgeon input.

Computer instructions of tool paths for machining the patient-specific spacers 200 can be generated and stored in a tool path data file. The tool path can be provided as input to a CNC mill or other automated machining system, and the patient-specific spacers 200 can be machined from solid or porous metals and/or alloys. The patient-specific spacers 200 can also be manufactured from powder metal using rapid prototyping methods, such as, for example, stereolithography, laser deposition sintering or other such methods. The patient-specific spacers 200 can be sterilized and shipped to the surgeon or medical facility for use during the surgical procedure in a patient and surgeon specific kit. In addition to the patient-specific spacers 200, the kit can include the acetabular cage 100, an acetabular cup liner or other articulating bearing for the femoral head (not shown), various fixation screws and fasteners, various non-custom or patient-specific augments for the acetabular cup (dome) 102, as well as a selection of instruments generally used for the surgical procedure or specifically requested by the surgeon. The instruments in the kit can include an acetabular cup inserter and/or impactor, a reamer, various flange benders, vise grip instruments and other instruments for the surgical procedure, such as those commercially available from Biomet Manufacturing Corp., Warsaw, Ind. Patient-specific augments for the dome of the acetabular cup 102 are described in commonly assigned U.S. patent application Ser. No. 12/978,069, filed Dec. 23, 2010, the disclosure of which is incorporated herein by reference.

Referring to FIGS. 8 and 9, patient-specific spacers 400 can be similarly constructed for another exemplary acetabular cage 300 that is used in acetabular reconstruction. Acetabular cages similar to acetabular cage 300 are commercially available Biomet Manufacturing Corp., Warsaw, Ind. The acetabular cage 300 can include an acetabular cup or shell 302 having a cup rim 310, an ischial blade 330 extending from a first outer slot 312 of the acetabular cup 302, an obturator foramen hook 332 extending from a second outer slot 312 of the acetabular cup 302 and a bifurcated iliac flange 333 that includes a common first (proximal) portion 334 extending from the cup rim 310 and first and second distal flange portions 336, 338 extending from the common first portion 334. In this embodiment of the acetabular cage 300, the ischial blade 330, the obturator foramen hook 332 and the bifurcated iliac flange 333 are removably coupled to the acetabular cup 302 by snap-fit and/or by using, for example, screws or other fasteners and are selectively included in the prosthesis at the discretion of the surgeon. For example, in the environmental view of FIG. 9 only the bifurcated iliac flange 333 and the obturator foramen hook 332 are shown. An exemplary fastener 342 coupling the obturator foramen hook 332 to the acetabular cup 302 is shown in the view of FIG. 8 and a similar fastener can be used for the ischial blade 330 (hidden from view). The first portion 334 of the bifurcated iliac flange 333 can also be attached with fasteners to a corresponding extension 309 of the cup rim 310.

The acetabular cup 302 and the ischial blade 330 can be made from a titanium alloy (such as Ti-6Al-4V, for example). The convex (bone-engaging surface of the acetabular cup 302 can be coated with porous coating, such as a titanium alloy plasma spray porous coating commercially available from Biomet Manufacturing Corp., Warsaw, Ind. The obturator foramen hook 332 and the bifurcated iliac flange 333 can be made from pure titanium or other metal. The obturator foramen hook 332 can be crimped by the surgeon during implantation. The bifurcated iliac flange 333 can also be bent during implantation. In other embodiments, the bifurcated iliac flange 333 can also be made of titanium alloy and have a greater thickness when used with the patient-specific spacers 400 because, as discussed above in connection with the spacers 200, each patient-specific spacer 400 is also designed preoperatively to register in only one position and nestingly mate (as a negative) with the underlying iliac surface of the specific patient and provide rigidity and support on the corresponding iliac surface without the need to bend the iliac flange 333. Apart from the fact that the spacers 400 are designed to receive the corresponding first and second distal flange portions 336, 338 of the bifurcated iliac flange 333, the spacers 400 are similar to the spacers 200 and the description of similar features is not repeated. For example, each patient-specific spacer 400 has a recess 407 that receives a corresponding distal iliac flange portion 336, 338 and an opposite patient-specific surface 420 configured during the preoperative plan to mate to a corresponding iliac anatomy of the pelvis 80 of the patient and register in only one position.

In some embodiments, an entire flange can be preoperatively designed to be patient-specific to nestingly conform to the specific patient's periacetabular anatomy in a single position, without the need of intraoperative bending or other deformation by the surgeon. In this respect, the patient-specific flange can be designed with adequate thickness for stability and rigidity and without using any spacers. An exemplary patient-specific flange 500 is illustrated in FIG. 10. The patient-specific flange 500 can be modularly or removably connected to an acetabular cup 302 (shown generically). In some embodiments, the patient-specific flange 500 can have a connecting portion 520 with an opening 502 for receiving a fastener 514 from a corresponding connecting portion 311 of the acetabular cup 311, although other types of modular connectors can be used, such as tongue-and-groove with or without screws, etc.

The patient-specific flange 500 has first and second opposing surfaces 504, 506. The first surface 504 is configured as a patient-specific surface that mirrors (as a negative surface) the corresponding pelvic anatomy of the patient. Accordingly, the width or thickness “t” of the flange between the first and second surfaces 540, 506 can be variable in a patient-specific manner. The patient-specific flange 500 is shown generically with two fixation holes 510, although it will be appreciated that the patient-specific flange 500 can be designed with different number of and arrangement of fixation holes and overall shape. The modular patient-specific flange 500 can be used in an acetabular cage (100, 300) that includes additional non custom flanges and patient-specific spacers (200, 400) for the non-custom flanges, as described above. In this respect, the patient-specific flange 500 can replace one of the non-custom flanges of the acetabular cage

Summarizing, the present teachings provide various patient-specific spacers 200, 400 that can be included in a kit for acetabular revision surgery for a specific patient. The patient-specific spacers 200, 400 are designed during a preoperative surgical plan of the patient based on a three dimensional digital image of the pelvic anatomy of the patient that is constructed using commercially available software from medical scans of the patient. The design and construction of the patient-specific spacers 200, 400 are made preoperatively in conjunction and coordination with the selection of an appropriate acetabular cage for the patient. A plurality of patient-specific spacers 200, 400 can be included in the kit. The patient-specific spacers 200, 400 combine patient-specific customization with rigidity and reinforcement for the flanges of the acetabular cage and can relieve the surgeon from the need to bend corresponding flanges of the acetabular cages intraoperatively for engagement with the pelvis of the specific patient. In this respect, the patient-specific spacers can facilitate and possibly streamline some acetabular reconstruction procedures. In some embodiments, modular patient-specific flanges for use without spacers can also be included in the kit.

Example embodiments are provided so that this disclosure is thorough, and fully conveys the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure.

It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. Accordingly, individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

1. A pelvic implant system comprising: an acetabular cage implantable into a pelvis of a patient; the acetabular cage including an acetabular cup, and an iliac flange and an ischial flange coupled to an upper portion of the acetabular cup; and an iliac spacer and an ischial spacer, wherein each of the iliac and ischial spacers comprises first and second opposing surfaces, and a peripheral surface located between and to space apart the first and second surfaces to provide at least one of the iliac and ischial spacers with a wedge shape, wherein each of the first surfaces is shaped to receive a complementary-shaped portion of a corresponding flange of at least one flange of the iliac and ischial flanges, wherein each of the second surfaces defines a patient-specific bone-engaging surface preoperatively configured from a three-dimensional image of the pelvis to complementary mate and closely conform to a surface of the pelvis under the flange in one position.
 2. The pelvic implant system of claim 21, wherein each of the peripheral surfaces includes a ridge surrounding each of the recesses that are elevated relative to each of the first surfaces.
 3. (canceled)
 4. (canceled)
 5. The pelvic implant system of claim 21, wherein at least the iliac flange includes a substantially square shape or square-like shape.
 6. The pelvic implant system of claim 5, wherein the recess of the iliac spacer has an elongated rectangular shape.
 7. The pelvic implant system of claim 5, wherein the recess of the iliac spacer has a square shape.
 8. The pelvic plant system of claim 21, wherein the recess of the ischial spacer as a triangular shape.
 9. The pelvic implant system of claim 1, wherein at least one flange of the iliac and ischial flanges is removably coupled to the acetabular cup.
 10. The pelvic implant system of claim 9, wherein the at least one flange of the iliac and ischial flanges that is removably coupled to the acetabular cup is an ischial blade modularly coupled to the acetabular cup.
 11. The pelvic implant system of claim 1, further comprising: an obturator foramen hook modularly coupled to the acetabular cup.
 12. The pelvic implant system of claim 1, wherein the iliac spacer includes a plurality of iliac spacers, wherein each iliac spacer of the plurality of iliac spacers includes a height different from the other iliac spacers such that the plurality of iliac spacers has a variable height.
 13. A pelvic implant system comprising: a patient-specific spacer having: a first surface with a recess configured for receiving at least a portion of a flange of an acetabular cage, wherein the acetabular cage is configured to be placed in an acetabular socket of a pelvis; a patient-specific second surface opposite to and spaced apart from the first surface, the patient-specific second surface preoperatively configured from a three-dimensional digital image of the pelvis to have a mirror surface that complementary mates and closely conforms to a surface of the pelvis under the flange in only one position on the pelvis; and a peripheral surface located between the first surface and the patient-specific second surface such that the first surface and the patient-specific second surface are angled relative to each other such that the patient-specific spacer has a substantially wedge shape.
 14. The pelvic implant system of claim 13, wherein the patient-specific spacer includes a plurality of patient-specific spacers, wherein each of the patient-specific spacers includes a peripheral surface that has a height; wherein the height of each patient-specific spacer is different from each of the other patient-specific spacers, such that the plurality of patient-specific spacers has a variable height.
 15. The pelvic implant system of claim 14, wherein each of the plurality of patient-specific spacers includes a recess that is at least one of triangle-shaped, elongated rectangle-shaped, substantially square-shaped, or square-shaped.
 16. The pelvic implant system of claim 15, wherein the recesses are configured for at least one ischial flange and at least one iliac flange. 17.-20. (canceled)
 21. The pelvic implant system of claim 1, wherein each of the first surfaces has a recess configured to receive the complementary-shaped portion of the corresponding flange.
 22. The pelvic implant system of claim 1, wherein the acetabular cup has a rim that lies substantially in a plane, wherein the iliac flange and the ischial flange are angled away from the acetabular cup relative to the plane.
 23. The pelvic implant system of claim 22, wherein the wedge shape of the at least one of the iliac and ischial spacers has a wide end and a narrow end, and the narrow end is disposed proximate the acetabular cup and the wide end is disposed distal to the acetabular cup.
 24. The pelvic implant system of claim 2, wherein: a thickness of the iliac spacer is greater than a thickness of the iliac flange and a surface area of the iliac spacer is greater than a surface area of the iliac flange; and a thickness of the ischial spacer is greater than a thickness of the ischial flange and a surface area of the ischial spacer is greater than a surface area of the ischial flange.
 25. The pelvic implant system of claim 13, wherein the patient-specific spacer includes a plurality of fixation holes extending from the first surface to the patient-specific second surface.
 26. The pelvic implant system of claim 13, wherein the peripheral surface includes a ridge surrounding the recess that is elevated relative to the first surface. 